Study On Tire Properties Under Combined Conditions With Dynamic Friction Distribution Over The Contact Patch

Tire mechanical characteristics are the foundation of vehicle dynamics research. Compared with low speed condition, tire performance is different on high speed condition, such as decline of force, opposition of the aligning torque, abnormal tire wear and blown tire, which are all related to tire dynamic friction characteristics; tire dynamic friction characteristics under combined conditions have become the focus of attention, as complexed conditions with steering and braking are often existed when using the vehicle.The distribution of velocity and infinitesimal element friction force are very complicated as the physical structure and rubber material properties of tire are involute. Therefore, this paper studies the friction characteristics of tread rubber firstly, then this paper studies the dynamic friction distribution and its influence on tire force under combined conditions through tire theoretical model and experimental study. This paper has done some research on the following aspects:Firstly, perform the experimental research on rubber dynamic friction. Dynamic friction test under different velocities, pressure and pavements is performed. Modified Savkoor dynamic friction model is built considering the vertical load and velocity, and test data is identified.Secondly, build a cornering complex theoretical model. Carcass elasticity is introduced based on the cornering brush model, according to the deformation of carcass and tread, tire force formula is deduced without considering tread slipping. Then sliding velocity in slip zone is analyzed and its computing method is given out. Theoretical model considering dynamic friction characteristics is built, which can reflect the trend of decreasing lateral force under big side slip angle and increasing aligning torque towards negative direction, and direct the modeling of tire semi-empirical model.Thirdly, build a discrete simulation model under combined slip. The tire contact patch is discretized through the discrete simulation model, in order to solve the problem of the theoretical model considering the distribution of dynamic friction under combined conditions is too complex to resolve. Tire force is calculated through integration. With combined slip discrete simulation model, the formula of sliding velocity in slip zone is deduced. The direction of infinitesimal element tangential force in slip zone under combined conditions is researched. Then force and moment is obtained through reciprocating iteration. The discrete simulation model can describe the distribution of velocity and dynamic friction over the contact patch, it reveals the influence of dynamic friction distribution on tire force under combined conditions and achieves the goal of expressing variation of the total shear direction. These conclusions have a guiding significance on the modeling of semi-empirical model under combined conditions.Finally, perform the research on semi-empirical model considering the velocity and dynamic friction characteristics under combined conditions. The relationship between the cornering or longitudinal sliding stiffness, arguments of aligning torque arm and velocity and dynamic friction characteristics is built, then the cornering stiffness and the total shear direction is revised, analytical conclusion is introduced into the existing semi-empirical model, which enhancing the expression ability in different velocities of Uni Tire model under combined conditions. According to the result of the identification of test data, tire mechanical characteristics under combined conditions can be accurately expressed with the built semiempirical model.